A new inlet of the gypsum hydrocyclone with separation block and guide plate was presented in this paper. The particle trajectories in conventional hydrocyclone and particle movements in new inlet were simulated by computational fluid dynamics (CFD) with the Reynolds stress model (RSM) and discrete phase model (DPM). The simulated results showed that both particle moving radius and distance increased when the particle diameter became greater. Gypsum particles with variable size were separated at the new type of inlet

which was beneficial to the classification performance of the hydrocyclone. Experiments were carried out in order to have further understanding of the new inlet. It was found that the classification efficiency of particles with the diameter between 10 and 30 μm was obviously improved about 15% compared to the conventional hydrocyclone. The classification efficiency of particles with the diameter less than 6 μm presented a certain drop. At the same time

the density of underflow slurry increased apparently.